The present invention relates to sewing machines, and more particularly to a sewing machine provided with a needle bar disconnecting mechanism and a thread cutting mechanism. The former mechanism is provided for halting the vertical reciprocal movements of a needle bar to which a sewing needle is attached, and the latter mechanism is provided for cutting a needle thread and a bobbin thread.
Sewing machines having a lateral feeding mechanism in addition to a forward feeding mechanism to stitch embroidery or large decorative patterns have been known, as disclosed in copending U.S. patent application Ser. No. 07/525,765 now U.S. Pat. No. 4,995,328 assigned to the same assignee. A workpiece fabric on a throat plate of the sewing machine is moved in the forward direction by the forward feeding mechanism and moved in a lateral direction orthogonal to the forward direction by the lateral feeding mechanism. It is thus necessary that the vertical reciprocal movements of the needle bar be temporarily stopped during the lateral movements of the workpiece fabric. To this end, a needle bar disconnecting mechanism has conventionally been employed which is interposed between an arm spindle and a needle bar for disconnecting the latter from the former.
One example of such needle bar disconnecting mechanisms is disclosed in Japanese Laid-Open Utility Model Publication No. 62-139472. According to the mechanism disclosed therein, a clutch is provided for isolating the needle bar from a needle bar gripper by swinging the needle bar with a stepping motor a width longer than a zigzag stitching width.
On the other hand, sewing machines of the type having a thread cutting mechanism driven by a sewing motor have been known, as disclosed in U.S. Pat. No. 4,592,297. The thread cutting mechanism is disposed beneath a throat plate for automatically cutting threads at the termination of stitching. In such a type of sewing machine, it is necessary that the reciprocal movements of the needle bar be stopped after actuation of the thread cutting mechanism to prevent a sewing needle from sticking in a workpiece fabric due to inertia of the sewing motor after the threads have been cut. To this end, conventional sewing machines are provided with a clutch between the sewing motor and an arm spindle for disconnecting the needle bar from the sewing motor after the thread cutting mechanism is actuated.
However, the provision of the clutch used in conjunction with the thread cutting increases the number of components or parts of the sewing machine despite the fact that the clutch is used only when the threads are cut.